In one aspect, the present invention relates to a process for preparing water-in-oil explosive emulsion compositions. In another aspect, the present invention relates to apparatus for the continuous production of cap sensitive or blasting agent water-in-oil explosive emulsion compositions on the commercial level. In still a further aspect, the present invention relates to a process for manufacturing explosive emulsion compositions including safety and quality control features further described hereinbelow.
Emulsion explosive compositions have recently obtained wide acceptance in the explosive industry because of their excellent explosive properties and ease of use in various applications. Until recently, water-in-oil explosives generally comprised blasting agents requiring a booster in order to effect their detonation. These emlsion type blasting agents were first disclosed by Bluhm in U.S. Pat. No. 3,447,978. While such emulsion type blasting agents have many advantages over other water slurry type blasting agents they are not cap sensitive. Cap sensitive emulsion explosives have been prepared in the past by the addition of an explosive ingredient or a specific detonation catalyst. Examples of these types of cap sensitive emulsion explosives are described in U.S. Pat. No. Re. 28,060. U.S. Pat. No. 3,770,522 and U.S. Pat. No. 3,765,964.
Recently it has been discovered that a cap sensitive water-in-oil emulsion explosive composition, which can be detonated with a No. 6 cap at diameters of 1.25" and lower, which does not contain an explosive ingredient or a detonation catalyst can be formulated by employing closed cell void containing materials, such as microbubbles fabricated from saran or glass, with specific proportions of a hydrocarbon fuel component, an emulsifier, water, inorganic oxidizing salts, and optionally, an auxiliary fuel, such as aluminum. These cap sensitive water-in-oil explosive compositions are described in detail in U.S. patent application Ser. No. 740,094 filed Nov. 9, 1977.
Processes for preparing occluded air sensitized water-in-oil emulsion blasting agents, which are noncap sensitive, as well as cap sensitive compositions are known in the prior art. Such processes have a limited disadvantage in that because the products depend on occluded air for sensitization, process conditions when admixing the aqueous oxidizing salt solutions thereof with the hydrocarbon fuel component thereof must be closely controlled. Temperature conditions within such processes must be regulated such that the aqueous oxidizing salt solution does not reach a temperature so low so as to cause crystallization and salting out of the inorganic oxidizing salts in the solution. However, the process must be operated at temperatures low enough such that the hydrocarbon fuel components, employed as the oil phase of the water-in-oil emulsion, are sufficiently congealed so as to provide for occlusion of air therein.
The process for preparation of water-in-oil emulsion explosive compositions which are cap sensitive such as those described above and disclosed in U.S. application Ser. No. 740,094 does not require that the hydrocarbon fuel component be at a congealing temperature since these explosive emulsion compositions do not rely upon occluded air for sensitization. However, water-in-oil explosive compositions which are cap sensitive present a higher hazard, from a production standpoint, since the increased sensitivity increases the risk of inadvertent detonation of the compositions during processing.
Therefore, a relatively safe and efficient method for producing cap sensitive water-in-oil explosive emulsions on a commercial scale is desirable and such a process presents problems of a different nature than those overcome by prior art processes dealing with the production of occulded air sensitized emulsion explosive compositions.